Can I use if pointer instead of if pointer NULL

Question

Is it safe to check a pointer to not being NULL by writing simply if pointer  or do I have to use if pointer    NULL

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Is it safe     is a question about the language standard and the generated code    Is is a good practice   is a question about how well the statement is understood by any arbitrary human reader of the statement  If you are asking this question  it suggests that the  safe  version is less clear to future readers and writers

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Yes  you can  The ability to compare values to zeros implicitly has been inherited from C  and is there in all versions of C    You can also use if   pointer  to check pointers for NULL

User · Answer

I think as a rule of thumb  if your if-expression can be re-written as  const bool local predicate    if-expression   if  local predicate        such that it causes NO WARNINGS  then THAT should be the preferred style for the if-expression    I know I get warnings when I assign an old C BOOL   define BOOL int  to a C   bool  let alone pointers

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As others already answered well  they both are interchangeable   Nonetheless  it s worth mentioning that there could be a case where you may want to use the explicit statement  i e  pointer    NULL   See also https   stackoverflow com a 60891279 2463963

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Yes  you could    A null pointer is converted to false implicitly a non-null pointer is converted to true    This is part of the C   standard conversion  which falls in Boolean conversion clause      4 12 Boolean conversions     A prvalue of arithmetic  unscoped enumeration  pointer  or pointer to member type can be converted to a prvalue of type bool  A zero value  null pointer value  or null member pointer value is converted to false  any other value is converted to true  A prvalue of type std  nullptr t can be converted to a prvalue of type bool  the resulting value is false

User · Answer

Yes  you can  In fact  I prefer to use if pointer  because it s simpler to read and write once you get used to it   Also note that C  11 introduced nullptr which is preferred over NULL

User · Answer

yes  of course   in fact  writing if pointer  is a more convenient way of writing rather than if pointer    NULL  because  1  it is easy to debug 2  easy to understand 3  if accidently  the value of NULL is defined  then also the code will not crash

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Yes  Both are functionally the same thing  But in C   you should switch to nullptr in the place of NULL

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Yes  you can always do this as  IF  condition evaluates only when the condition inside it goes true  C does not have a boolean return type and thus returns a non-zero value when the condition is true while returns 0 whenever the condition in  IF  turns out to be false  The non zero value returned by default is 1  Thus  both ways of writing the code are correct while I will always prefer the second one

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Question is answered  but I would like to add my points    I will always prefer if pointer  instead of if pointer    NULL  and if  pointer  instead of if pointer    NULL      It is simple  small  Less chances to write a buggy code  suppose if I misspelled equality check operator    with   if pointer    NULL  can be misspelled if pointer   NULL  So I will avoid it  best is just if pointer    I also suggested some Yoda condition in one answer  but that is diffrent matter  Similarly for while  node    NULL  amp  amp  node- gt data    key   I will simply write while  node  amp  amp  node- gt data    key  that is more obvious to me  shows that using short-circuit    may be stupid reason  Because NULL is a macro  if suppose  some one redefine by mistake with other value

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Yes  In fact you should  If you re wondering if it creates a segmentation fault  it doesn t

User · Answer

The relevant use cases for null pointers are   Redirection to something like a deeper tree node  which may not exist or has not been linked yet  That s something you should always keep closely encapsulated in a dedicated class  so readability or conciseness isn t that much of an issue here  Dynamic casts  Casting a base-class pointer to a particular derived-class one  something you should again try to avoid  but may at times find necessary  always succeeds  but results in a null pointer if the derived class doesn t match  One way to check this is  Derived  derived ptr   dynamic cast lt Derived  gt  base ptr   if derived ptr    nullptr             or  preferrably  auto derived ptr         Now  this is bad  because it leaves the  possibly invalid  i e  null  derived pointer outside of the safety-guarding if block s scope  This isn t necessary  as C   allows you to introduce boolean-convertable variables inside an if-condition   if auto derived ptr   dynamic cast lt Derived  gt  base ptr             which is not only shorter and scope-safe  it s also much more clear in its intend  when you check for null in a separate if-condition  the reader wonders  ok  so derived ptr must not be null here    well  why would it be null   Whereas the one-line version says very plainly  if you can safely cast base ptr to Derived   then use it for       The same works just as well for any other possible-failure operation that returns a pointer  though IMO you should generally avoid this  it s better to use something like boost  optional as the  container  for results of possibly failing operations  rather than pointers    So  if the main use case for null pointers should always be written in a variation of the implicit-cast-style  I d say it s good for consistency reasons to always use this style  i e  I d advocate for if ptr  over if ptr  nullptr      I m afraid I have to end with an advert  the if auto bla        syntax is actually just a slightly cumbersome approximation to the real solution to such problems  pattern matching  Why would you first force some action  like casting a pointer  and then consider that there might be a failure    I mean  it s ridiculous  isn t it  It s like  you have some foodstuff and want to make soup  You hand it to your assistant with the task to extract the juice  if it happens to be a soft vegetable  You don t first look it at it  When you have a potato  you still give it to your assistant but they slap it back in your face with a failure note  Ah  imperative programming   Much better  consider right away all the cases you might encounter  Then act accordingly  Haskell   makeSoupOf    Foodstuff - gt  Liquid makeSoupOf p  Potato        mash  boil p   lt  gt  water makeSoupOf vegetable    isSoft vegetable    squeeze vegetable  lt  gt  salt makeSoupOf stuff    boil  throwIn  water lt  gt salt  stuff    Haskell also has special tools for when there is really a serious possibility of failure  as well as for a whole bunch of other stuff   monads  But this isn t the place for explaining those    langle  advert rangle

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You can  the null pointer is implicitly converted into boolean false while non-null pointers are converted into true  From the C  11 standard  section on Boolean Conversions      A prvalue of arithmetic  unscoped enumeration  pointer  or pointer to member type can be converted to a   prvalue of type   bool  A zero value  null pointer value  or null member pointer value is converted to   false    any other value is converted to   true     A prvalue of type   std  nullptr t   can be converted to a prvalue of   type   bool     the resulting value is   false

User · Answer

Explicitly checking for NULL could provide a hint to the compiler on what you are trying to do  ergo leading to being less error-prone

[c++] Can I use if (pointer) instead of if (pointer != NULL)?

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